The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Controllers having proportional gain and integral gain components in a control loop structure are well known. Variations of these controllers can include a differential gain component as well. However, a controller using a proportional and integral (PI) control loop structure can exhibit excessive output overshoot resulting from “integrator wind-up.”
By way of example only, a power amplifier can include a PI type controller and can provide power to an electrical load. In the case of an inductive load, again by example, voltage is applied across the inductor for a time proportional to the inductance and inversely proportional to the applied voltage. During this time, a system error (desired value versus actual value) can exist, resulting in an erroneously high integrator value. The integrator value achieves a level in excess of a level required to maintain steady-state output current. The result is transient current overshoot as illustrated in FIG. 1. FIG. 1 illustrates, for example, a 17% overshoot at 10 in response to a first command signal slew rate, while a second overshoot of 2% is indicated at 12 for a corresponding command signal having a slower slew.
Typically, in order to minimize overshoot, it is known to reduce the integrator value of the integrator component and/or increase the proportional value of the proportional component. Although this technique reduces overshoot, it has the disadvantage of increasing settling time, which is the time that the controller needs to obtain the desired steady state value. In FIG. 2, a command signal is indicated at 14, wherein a first output signal corresponding to a higher integrator gain value is indicated at 16, while a second output signal 18 for a lower integrator value is also illustrated. As can be seen in FIG. 2, the overshoot or the second or lower of the second output signal 18 having the lower integrator gain value is less than the overshoot of the first output signal; however, the settling time, Tlow gain for the lower integrator gain value is substantially longer than the settling time, Thigh gain for the high gain value.